Even as a Tank spec assassin I was finally able to beat her but you have to kite, LOS, use knock backs and lots of ranged attacks and interrupts.
It's very important that you get out of her AOE and interrupt or KB them when possible if not, taunt her and run away and use LOS to make her come after you while Khem was still swinging away at her. I used lots of Shocks and Force Lightening and taunt swapped between myself and Khem.
If you get into trouble you should vanish and reset .. I mean force cloak.
This was the spec I was using but it definitely wasn't easy.
http://www.torhead.com/skill-calc#200rcrokRsz.1